EP2467343B1 - Inductively heated hob having a metal-coated cover plate - Google Patents

Description

The invention is based on a hob with a metallically coated cover plate according to the preamble of claim 1 and a method for producing such a cover plate according to the preamble of claim 11.

From the US 2008/0264931 A1 a hob with a cover plate is known, which is designed to cover one or more heating elements. The cover plate is based on a base of glass or glass ceramic, which is equipped on at least one side with a metallic layer to improve the aesthetic design options for such a hob.

From the DE 10 2006 017 250 A1 a cooking device with a disk unit is known. On a lower side of the plate unit, a coating may be applied, which has a metal-like layer and a decorative section. The metal-like layer can be applied over its entire area in a surface area that corresponds to a functional zone, wherein a food preparation vessel can be set up on a functional zone on an upper side of the plate unit.

From the US 2008/0190409 A1 is a hob plate known, on the underside also a coating can be applied. It can be provided that in a surface area on which a preparation vessel can be placed at the top, a metallic layer is applied, this area is surrounded by a line-shaped ink layer.

Furthermore, induction hobs with a plurality of inductors arranged under a cover plate are known, which generate a high-frequency alternating magnetic field. The alternating magnetic field penetrates the cover plate and generates eddy currents in a cooking pot placed on the hob or in the bottom thereof. These eddy currents heat the soil in the desired manner.

Metals shield magnetic fields very effectively. Therefore, the technical prejudice exists that the use of metallically coated cover plates for induction hobs is unfavorable. Even if metal layers with a layer thickness less than the penetration depth of the magnetic field are used, the currents induced by the magnetic field in the layer lead to uncontrolled and unwanted electromagnetic radiation, which can degrade the electromagnetic compatibility of the device and the fulfillment of relevant standards difficult to electromagnetic compatibility.

The invention is therefore in particular the object to improve the electromagnetic compatibility of a cooktop with a metallic layer and to provide a method for producing a cover plate for such a hob.

The object is achieved in particular by a hob with the features of independent claim 1 and by a method according to independent claim 11. Advantageous embodiments and modifications of the invention will become apparent from the dependent claims.

The invention is particularly based on a hob with at least one heating inductor and a cover plate made of glass or glass ceramic, which has on at least one side a coating with a metallic layer.

It is proposed that a coverage area of the metallic layer covering the heating inductor be electrically isolated from a surrounding area of the layer surrounding the coverage area. As a result, it can be avoided that induced currents are exchanged between the covering area and the surrounding area. The maximum oscillation amplitude of charges in the metallic layer is thereby limited, which ultimately leads to a reduced radiation intensity. The electromagnetic compatibility of the hob is thereby improved and compliance with the relevant standards is also possible with a combination of a metal-coated cover plate with Heizinduktoren.

A further reduction of the electromagnetic emissions can be achieved if the coverage area comprises a plurality of electrically isolated subregions. The subregions are arranged concentrically to each other and can in a particular advantageous embodiment of the invention have the form of concentric rings, which may additionally have one or more interruptions in the circumferential direction.

The hob may be a pure induction hob or a hob with various heating elements, which may include, for example, both inductors and radiant heaters.

In particular, if the thickness of the metallic layer is only a fraction of less than 50%, particularly advantageously less than 10% of a magnetic penetration depth of the magnetic field generated by the heating inductor in the material of the metallic layer, despite the metallic layer, a sufficient coupling of the heating inductor the cookware element can be achieved. The magnetic penetration depth is typically between 10 and 100 nm and describes the exponential decay of the magnetic field in a metallic body. The penetration depth is also called London's penetration depth.

An effective insulation with a decorative overall impression can be achieved if the coverage area is limited by a linear interruption of the layer. The interruption may in particular be circular, oval or of the shape of a regular polygon.

The interruption is clearly visible and thus suitable for visualizing or limiting the heating zone formed by the heating element, if a width of the interruption is at least 2 mm. Even with a width of at least 1 mm, good visibility of the interruption line can be ensured against the otherwise metallic background of the layer.

In order to improve the visibility of the interruption, it is further proposed that a dielectric ink layer is applied to the cover plate, at least in the region of the interruption.

The dielectric ink layer may simultaneously act as a protective layer for the metallic layer if the dielectric ink layer at least partially covers the metallic layer.

The metallic layer may in particular be applied to a rear side of the cover plate. As a result, damage to the metallic layer can be avoided.

The interruption can be produced, for example, during the application of the metallic layer by the application of a mask, or alternatively the metallic layer can be removed in the area of the interruption. For this purpose, the metallic layer can be removed either mechanically or with a laser.

Another aspect of the invention relates to a method of manufacturing a cover plate of the type described above. It is proposed that for the electrical insulation of a covering the Heizinduktor coverage area of the metallic layer opposite an ambient region of the layer is incorporated into the metallic layer an interruption limiting the coverage area.

Further advantages emerge from the following description of the drawing. In the drawings, embodiments of the invention are shown. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

Fig. 1

ein Kochfeld mit einer Abdeckplatte nach einer ersten Ausgestaltung der Erfindung,

Fig. 2

eine Schnittdarstellung des Kochfelds aus Fig. 1,

Fig. 3

eine Abdeckplatte eines Kochfelds nach einer weiteren Ausgestaltung der Erfindung mit einem Überdeckungsbereich mit mehreren konzentrischen Teilbereichen, und

Fig. 4

einen ovalen Überdeckungsbereich nach einer weiteren Ausgestaltung der Erfindung.

Show it:

Fig. 1

a hob with a cover plate according to a first embodiment of the invention,

Fig. 2

a sectional view of the hob off Fig. 1 .

Fig. 3

a cover plate of a hob according to another embodiment of the invention with a covering area with a plurality of concentric portions, and

Fig. 4

an oval covering area according to a further embodiment of the invention.

Fig. 1 shows a hob with four Heizinduktoren 10, which are arranged under a cover plate 12 made of glass or glass ceramic. The heating inductors 10 are supplied with a high-frequency heating current and generate a high-frequency magnetic field during operation of the induction hob, which penetrates the cover plate 12 and penetrates into the bottom of a cooking utensil mounted on the hob. The eddy currents generated in the bottom of the cookware element finally heat this floor and thus the food received in the pan or the pan.

During operation, heat is transferred to the cover plate 12 in a region of the cover plate 12 covered by the bottom of the cooking pot through contact with the cookware element. As a result, the cover plate 12 is temperature resistant up to at least 200 or 300 ° C and permeable to that of must be the magnetic field generated by the heating inductor 10. Furthermore, the surface of the cover plate 12 must be robust and easy to clean.

Each of the heating inductors 10 is arranged in a circle and below each also a likewise circular coverage area 16 of the cover plate 12, which has the same diameter as the corresponding heating inductor 10. The coverage areas 16 correspond to the areas on which cooking pots should ideally be placed in order to ensure efficient operation of the To enable cooking hob. The size of the cooking pots should be at least about the size of the coverage areas 16. The covering areas 16 are delimited by a drawing applied to the back of the cover plate 12, which will be explained in more detail below. Alternatively, it is also possible to apply a marking which surrounds the covering region 16 on the upper side of the cover plate 12, for example in a screen printing process.

The covering regions 16 are in particular geometrically congruent with the shape of the heating inductors 10 and project beyond their contour in plan view by at most 1 cm. In essence, the contour of the coverage areas 16 follows the contour of the heating inductors 10.

Fig. 2 shows a sectional view of the hob after Fig. 1 in the region of such a boundary between a covering area 16 and a surrounding area 18, which surrounds the covering area 16.

The back of the cover plate 12 is provided with a coating with a metallic layer 14, which may be applied, for example, in a magnetron sputtering process. A thickness D of the metallic layer 14 is between about 5 and 40 nm and is thus less than 50% of a magnetic penetration depth of the magnetic field generated by the heating inductor 10 in the material of the metallic layer 14. The thickness D is in Fig. 2 greatly oversubscribed for better visualization and is in particularly advantageous embodiments of the invention less than 10% of the penetration depth.

The coverage area 16 is delimited by a linear interruption 20 of the layer 14. The interruption 20 delimits the coverage area 16 from the surrounding area 18 and forms the in Fig. 1 illustrated closed ring. The interruption 20 thus electrically isolates the coverage area 16 from the surrounding area 18 and prevents the eddy currents induced by the magnetic field between the coverage area 16 and the surrounding area 18 being exchanged. This improves the overall electromagnetic compatibility.

The width B of the interruption 20 is about 1-2 mm, so that the interruption 20 through the transparent material of the cover plate 12 visible from the front of the cover plate 12 as a clearly defined line with a width of 2 mm in the otherwise shiny metallic background is.

After the application of the metallic layer 14, a dielectric protective and / or colored layer 22 is applied to the cover plate 12 in the region of the interruption 20. The protective and / or color layer 22 prevents corrosion or damage to the metallic layer 14 and is also visible in the region of the interruption 20 from the front side of the cover plate 12. As a result of the color selection of the dielectric ink layer 22, it is thus possible to select the color of the markings delimiting the coverage areas 16. In order to protect the metallic layer 14 as well as possible, the dielectric protective and / or colored layer 22 can, in a particularly advantageous embodiment, cover the entire rear side of the cover plate 12.

Fig. 3 shows an alternative embodiment of the invention, in which the coverage area 16 comprises a plurality of electrically isolated portions 24. The sections 24 are in the form of concentric circles. As a result, the electromagnetic compatibility of the hob is further improved.

In the manufacture of the cover plate 12, the interruption 20 can be produced either by the application of a mask during the application of the metallic layer 14 or by the subsequent removal of the layer 14, for example by a laser ablation process. The isolation of the portions 24 from each other can be done, for example, when using a laser ablation process by very thin, linear interruptions. These interruptions can be very thin, for example in the range of a few micrometers, so that they do not disturb the overall impression of the covering region 16 as a closed metallic surface.

Fig. 4 shows a further embodiment of the invention with an oval coverage area 16 for covering a pair of inductors, which together can operate as a roaster heating zone. The coverage area 16 here also comprises a plurality of electrically isolated partial areas 24, which are adapted to the heating inductors 10.

In further embodiments of the invention, the cover plate may be provided with a plurality of metallic layers, which may also be semitransparent.

reference numeral

10

heating inductor

12

cover

14

layer

16

coverage area

18

surrounding area

20

interruption

22

coat of paint

24

subregion

B

width

D

thickness

Claims (11)

1. Hob which comprises at least one heating inductor (10) and a glass or glass ceramics cover plate (12) that is coated with a metal layer (14) on at least one side thereof, wherein
   a cover region (16) of the metal layer (14) covering the heating inductor (10) is electrically insulated from a surrounding region (18) of the layer (14), which surrounding region (18) surrounds the cover region (16), characterised in that the cover region (16) comprises a plurality of sections (24) which are electrically insulated from each other and the sections (24) are arranged concentrically to each other.
2. Hob according to claim 1, characterised in that a thickness (D) of the metal layer (14) makes up less than 50 % of a magnetic penetration depth of the magnetic field produced by the heating inductor (10) into the material of the metal layer (14) and is between 5nm and 40nm.
3. Hob according to claim 2, characterised in that the thickness (D) of the metal layer (14) is less than 10 % of a magnetic penetration depth of the magnetic field produced in the heating inductor (10) in the material of the metal layer (14).
4. Hob according to any one of the preceding claims, characterised in that the cover region (16) is limited by a linear interruption (20) in the layer (14).
5. Hob according to claim 4, characterised in that a width (B) of the interruption (20) is at least 2 mm.
6. Hob according to any one of the preceding claims, characterised in that a dielectric coloured layer (22) is applied to the cover plate (12) at least in the region of the interruption (20).
7. Hob according to claim 6, characterised in that the dielectric coloured layer (22) at least partially covers the metal layer (14).
8. Hob according to any one of claims 4 to 7, characterised in that the interruption (20) is produced by applying a mask during application of the metal layer (14).
9. Hob according to any one of claims 4 to 7, characterised in that the interruption (20) is produced by removing the layer (14) following application of the metal layer (14).
10. Hob according to any one of the preceding claims, characterised in that the sections (24) have the form of concentric rings.
11. Method for producing a glass or glass ceramics cover plate (12) for a hob, the cover plate (12) being coated with a metal layer (14) on at least one side thereof, wherein an interruption (20) limiting the cover region (16) is worked into the metal layer (14) to electrically insulate a cover region (16) of the metal layer (14) covering the heating inductor (10) from a surrounding region (18) of the layer (14), characterised in that the cover region (16) is embodied with a plurality of sections (24) which are arranged concentrically to each other and are electrically insulated from each other.

Images